docs: def current_ideal(P, V, phase=3, PF=1):
      r'''Returns the current drawn by a motor of power `P` operating at voltage
      `V`, with line AC of phase `phase` and power factor `PF` according to [1]_.
  
      Single-phase power:
  
      .. math::
          I = \frac{P}{V \cdot \text{PF}}
  
      3-phase power:
  
      .. math::
          I = \frac{P}{V \cdot \text{PF} \sqrt{3}}
  
  
      Parameters
      ----------
      P : float
          Power, [W]
      V : float
          Voltage, [V]
      phase : int, optional
          Line AC phase, either 1 or 3
      PF : float, optional
          Power factor of motor
  
      Returns
      -------
      I : float
          Power drawn by motor, [A]
  
      Notes
      -----
      Does not include power used by the motor's fan, or startor, or internal
      losses. These are all significant.
  
      Examples
      --------
      >>> current_ideal(V=120, P=1E4, PF=1, phase=1)
      83.33333333333333
  
      References
      ----------
      .. [1] Electrical Construction, and Maintenance. "Calculating Single- and
         3-Phase Parameters." April 1, 2008.
         http://ecmweb.com/basics/calculating-single-and-3-phase-parameters.
      '''
      if phase not in [1, 3]:
          raise Exception('Only 1 and 3 phase power supported')
      if phase == 3:
          return P/(V*3**0.5*PF)
      else:
          return P/(V*PF)